1. Field of Invention
The present invention relates generally to the sealing of contaminant-free housings, such as hard disk drive assembly housings and, more particularly, to the hermetic or near-hermetic sealing of input/output connectors used with contaminant-free housings.
2. Description of the Related Art
In order to insure a long service life for sensitive components, such as those contained in a hard disk drive, housings are often hermetically or near-hermetically sealed. Such sealing is generally effective in preventing the entry of contaminants into the assembly housing. However, hard disk drives and other sensitive components are often part of systems and, accordingly, must be electrically connected to other components within the system. The structure necessary to provide the electrical connection is often the source of contaminants.
Hard disk drives and other sensitive components are normally connected to the other components in a system through the use of a flex cable which includes a plurality of input/output leads that are electrically isolated from one another within a substantially flat, plastic cable. The electrical leads typically terminate on the pins of a bulkhead connector. The bulkhead connector is inserted into a connector slot provided on the housing, protrudes outside of the housing, and provides electrical access for connection to other components. Contaminants pass through the flex cable and bulkhead connector arrangement in two ways. First, inadequate sealing between the bulkhead connector and the connector slot often allows contaminants to enter the otherwise sealed housing. Second, the bulkhead connector includes bores through which power and signal pins extend to the flex cable. Contaminants can pass through the bores into the housing.
A number of solutions have been proposed in regards the problem of housing contamination associated with electrical connectors. For example, connectors meeting military specifications employ a glass bead seal between the pins and the bulkhead connector. While the glass bead seal effectively prevents contamination via the bulkhead bores, it obviously will not prevent ingress of contaminants caused by poor sealing between the bulkhead connector and connector slot. The glass bead seal is also prohibitively expensive for civilian use.
Another attempt to solve the aforementioned problem in the art involves the manual application of a sealing compound (normally Loctite.TM.) to each power or signal pin in the bulkhead connector. This solution, however, is labor intensive, costly, and subject to sealing failure. Inadequate sealing with respect to a single pin in the bulkhead connector can cause a sealing failure. Moreover, this proposed solution fails to address the problem of inadequate sealing between the bulkhead connector and connector slot.
A third method of sealing bulkhead connector pins, which involves injection molding various types of plastic material around the pins during the molding of the bulkhead, has also failed to solve the aforementioned problems in the art. Tests have shown that air-tight pin sealing is not achieved using this method.
There have been a number of attempts to provide adequate sealing between the connector and connector slot. For example, U.S. Pat. No. 5,257,941, issued to Lwee et al., discloses a U-shaped electrical connector employed between the sealed environment of a hard disk drive housing and external electrical components. Referring to FIGS. 6, 7 and 8 of the '941 patent, a rectangular aperture is provided at one end of a hard disk drive housing. The aperture is dimensioned to allow registration and insertion of one end of a rigid, U-shaped electrical connector. The other end of the U-shaped connector is inserted into a circuit board connector. Once inserted, the top portion of the connector is flush with the external surface of the housing. Sealant is then applied to a portion of the connector in order to seal any gaps between the connector and the housing. Because the U-shaped connector is rigid, it is useless in those instances where the disk drive housing and the circuit board connector are slightly misaligned relative to one another. Also, the application of sealant during the final assembly process adds time and expense to the assembly process and renders disassembly very difficult in the event the connector requires replacement.
U.S. Pat. No. 5,276,577, issued to Brooks et al., discloses a relatively simple, but labor intensive method of sealing a hard disk drive assembly housing. As illustrated in FIGS. 4a-c of the '577 patent, a base and cover assembly form a contaminant free environment. A flat cable from within the drive assembly extends outwardly from within the sealed environment and mates with a connector outside of the enclosure. A piece of double sided adhesive is adhered to the cover. The cable is folded against the adhesive. Metal foil sealing tape is then applied over the cable and the gap between the base and cover. Clearly, this multi-step process is also labor intensive and costly. Furthermore, experience has shown that this type of seal frequently leaks air at the two ends of the flex cable. Such leaks necessitate repair work that often results in flex cable damage due to the permanent nature of the sealing materials employed.